The proposed studies are designed to investigate the Norwalk-like agents of gastroenteritis. The prototype agent, the Norwalk agent, is a significant cause of viral gastroenteritis in humans of all age groups throughout the world. Little is known regarding the characteristics of the other recently described, antigenically distinct Norwalk-like agents: the Snow Mountain and Hawaii agents. A principal aim of these studies is to develop efficient and sensitive means of in vitro detection of these agents, employing immune electron microscopy and radioimmunoassays. Since the Norwalk-like agents have not been cultivated in vitro, intensive studies will be conducted to propagate these agents in organ and tissue culture systems. Purification and biochemical characterization of virions and soluble virus proteins will also be carried out, for detailed comparison of the several agents and for definitive classification. Techniques developed above will enable seroepidemiological studies to be performed, along with examination of the roles of Sbnw Mountain and Hawaii agents as causes of outbreaks of gastroenteritis of unknown etiology. This proposal should generate important information with which to develop control measures for a significant human illness, viral gastroenteritis.